Plotters and other line or graphics drawing apparatus using pens, such as ball point pens or capillary tube pens, often mount the pen within a pen holder, and the pen holder is in turn driven by an electromechanical actuator, such as a solenoid, between a raised non-drawing position and a lowered drawing position for applying the ink to create lines or graphics on sheet material or other types of receiving surfaces. Such apparatus require that the pen be given an adequate supply of ink during a drawing process to assure the production of high quality, gap free lines, and for operation at high drawing speeds, this usually requires that the ink supplied to the pen be pressurized.
One known type of system for supplying pressurized ink to a pen includes a separate, refillable ink reservoir which holds a large quantity of ink and pressurized air for pressurizing the ink within the reservoir. The pressurized air may be continuously supplied to the ink reservoir during usage of the pen by an air pump mounted on the plotter or like apparatus, or may be introduced as a precharge behind the ink in the reservoir. An ink supply tube is connected between the reservoir and the pen, and the pressurized air discharges the ink from the reservoir, through the supply tube and into the pen.
One disadvantage experienced with this type of system is that the ink supply tube can impose both lateral and vertical forces on the upper end of the pen, which can in turn cause the pen and pen holder to bind, and can otherwise impede movement of the pen when driven between its raised non-drawing and lowered drawing positions.
Accordingly, it is an object of the present invention to overcome the drawbacks and disadvantages of prior art ink supply tubes or conduits for supplying ink to pens on plotters and like apparatus for drawing lines or graphics on sheet material or other receiving surfaces.